This invention relates generally to pulsed radar systems. Specifically, the present invention relates to radar systems which process a received radar signal to indicate the presence of a moving target. More specifically, the present invention relates to radar systems which process received radar signals using pseudo-coherent techniques.
A pseudo-coherent radar system represents a noncoherent system because a non-coherent local oscillator down-converts a received radio frequency (RF) signal to an intermediate frequency (IF) signal. However, a pseudo-coherent radar system splits the intermediate frequency signal into two sub-signals. These two sub-signals are coherent relative to each other. One of the sub-signals is delayed relative to the other sub-signal, and the resulting sub-signals mix together to produce a Doppler signal.
Previous pseudo-coherent, moving target indicators occupy excessively large amounts of space, consume excessive power, and require individual calibration in order to operate properly. Hence, such systems are costly to manufacture and to operate.
The problems suffered by previous moving target indicators relate to the delay technique used to delay one sub-signal relative to the other. Lumped element delay lines or predetermined lengths of coaxial transmission lines or predetermined lengths of coaxial transmission lines typically achieve these delays. However, the coaxial transmission lines are bulky and not suitable for applications which require the use of minimal space. Further, the lumped element delay lines require special tuning for each delay line to compensate for piece part tolerances.
Surface acoustic wave (SAW) devices provide delays using only a relatively small space. However, conventional SAW devices tend not to be employed to solve the particular problems faced by psuedo-coherent moving target indicators.
The problems suffered by conventional pseudo-coherent, moving target indicators additionally relate to power splitting devices and amplifiers which process the received radar signal. Regardless of the particular delay technique used, prior moving target indicator systems use an excessive number of power splitting devices and gain stages. Thus, the cost and power consumption of the radar device increases.